1. Technical Field
The present disclosure relates to an X-ray fluorescence analyzer.
2. Description of the Related Art
X-ray fluorescence analysis is a technique of irradiating a sample with an X ray emitted from an X-ray source, and detecting fluorescent X-rays emitted from the sample by an X-ray detector, and performing qualitative analysis of the sample or quantitative analysis of a concentration, a film thickness, or the like based on the intensities of the fluorescent X-rays.
The constituent elements of the sample generate fluorescent X-rays having energies characteristic of the individual elements. Therefore, the spectra of the measured X rays are searched for peaks of the fluorescent X-rays characteristic of the individual elements, whereby it is possible to find out which elements are contained. This analysis is called qualitative analysis.
Meanwhile, quantitative analysis uses a fact that the intensity of the fluorescent X-ray of each constituent element which is obtained is determined by the relation between the state of the X ray with which a sample is irradiated and the amount of the corresponding element existing in the irradiation area. Specifically, first, a sample is irradiated with X rays having known X-ray states, that is, known X-ray intensities for each energy, and the intensities of fluorescent X-rays of individual elements generated as the results of the irradiation is measured, and then the amounts of the elements capable of making X rays with those intensities be generated is calculated.
In this calculation process, various methods are used. In every method, for the accuracy of the analysis, it is important that the amount and energy distribution of X-ray for irradiation matches with the premise of calculation. In concentration analysis, it is possible to cancel the influence to a certain extent in a case where the entire intensity increases while the energy distribution is kept. However, in film thickness calculation, it is difficult to distinguish between increase or decrease in intensity and increase or decrease in film thickness, and thus the influence of variation in X ray for irradiation is more serious.
Since it is practically almost impossible to prepare an X-ray irradiation system which is completely stable and has a precisely defined energy distribution, a technique of measuring a sample having a known composition and a known structure and calibrating a device using the intensity of an X ray obtained from the measurement is generally used. Therefore, device calibration is a very important technique for accurate quantitative analysis and being required to be performed routinely and accurately. Due to this request, there has been disclosed a configuration in which a sample for calibration is mounted on a shutter member and automatically performs calibration. An example of such configuration is disclosed in Japanese patent publication No. JP-A-S59(1984)-067449.
In X-ray fluorescence analysis, the size of an area to be measured is often to be one of major concerns. In general, the measurement area is defined by restricting an X-ray irradiation area. According to the sizes of samples which are measurement targets, various devices having irradiation areas in the order of several millimeter to several tens micrometer are provided. Among those devices, devices having particularly small irradiation areas use advanced technologies of a collimator which is a structure capable of blocking X rays and having tiny holes, a capillary X-ray optical element for focusing X rays on a tiny area by using a total reflection phenomenon of the inner surface of a hollow glass fiber, and the like.
It is known that a misalignment in the positional relation between a collimator or capillary X-ray optical element and an X-ray generator influences the intensities and energy distributions of X rays to be emitted. That is, it can be said that the positional relation of the constituent elements of each of those devices is an element which should be calibrated to have accurate quantitative analysis.
The configuration disclosed in the Japanese patent publication No. JP-A-S59(1984)-067449 allows to move a calibration sample mounted on a shutter member into an X-ray irradiation area, and calibrate intensity variation attributable to variation of an X-ray source for irradiation with an X ray, but the route of the X ray and the incident direction of the X ray to a detector are different from those of normal measurement. For this reason, there may be a problem that, in the strict sense, a measurement condition for calibration is different from a normal measurement condition, and it is not possible to calibrate variations attributable to every element.
Further, in devices using X-ray focusing elements such as poly-capillaries recently being in widespread use, a small position gap between a focusing element and an X-ray generating portion of an X-ray source is attributable to intensity variation, even if these mechanisms are disposed above the focusing element, device calibration inevitably may become incomplete.
Furthermore, in general, in order to reduce an X-ray irradiation area, it is preferable to reduce a distance between a focusing element and a sample. Therefore, it may be difficult to dispose a calibration below the focusing element.
For these reasons, devices using X-ray focusing elements may have a problem that they do not have means for automatically calibrating the devices.